Transducers are devices used for converting energy from one form to another to measure a physical quantity. A typical transducer converts mechanical force or acceleration into electromagnetic energy. A transducer is mechanically coupled to an object to measure its motion. When this motion is vibrational, usually only certain frequency ranges are of interest. In such cases, a sensor employs a transducer and some means of filtering out the unwanted frequencies. To achieve this filtering, the sensor normally includes: (a) a transducer providing an output signal with a broad frequency range and (b) an amplifying and filtering circuit that is electrically connected to the transducer's output and eliminates the unwanted frequencies outside a given frequency band of interest.
Existing sensors are designed for sensing either low-frequency vibrations or high-frequency vibrations. To obtain signals representing both the low-frequency vibrations and high-frequency vibrations, two sensors must be used.